/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.tsfile.file.metadata;

import org.apache.iotdb.tsfile.common.conf.TSFileConfig;
import org.apache.iotdb.tsfile.common.conf.TSFileDescriptor;
import org.apache.iotdb.tsfile.file.metadata.enums.MetadataIndexNodeType;
import org.apache.iotdb.tsfile.utils.Pair;
import org.apache.iotdb.tsfile.utils.ReadWriteForEncodingUtils;
import org.apache.iotdb.tsfile.utils.ReadWriteIOUtils;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;

public class MetadataIndexNode {

    private static final TSFileConfig config = TSFileDescriptor.getInstance().getConfig();
    private final List<MetadataIndexEntry> children;
    private long endOffset;

    /**
     * type of the child node at offset
     */
    private final MetadataIndexNodeType nodeType;

    public MetadataIndexNode(MetadataIndexNodeType nodeType) {
        children = new ArrayList<>();
        endOffset = -1L;
        this.nodeType = nodeType;
    }

    public MetadataIndexNode(
            List<MetadataIndexEntry> children, long endOffset, MetadataIndexNodeType nodeType) {
        this.children = children;
        this.endOffset = endOffset;
        this.nodeType = nodeType;
    }

    public List<MetadataIndexEntry> getChildren() {
        return children;
    }

    public long getEndOffset() {
        return endOffset;
    }

    public void setEndOffset(long endOffset) {
        this.endOffset = endOffset;
    }

    public MetadataIndexNodeType getNodeType() {
        return nodeType;
    }

    public void addEntry(MetadataIndexEntry metadataIndexEntry) {
        this.children.add(metadataIndexEntry);
    }

    public boolean isFull() {
        return children.size() >= config.getMaxDegreeOfIndexNode();
    }

    MetadataIndexEntry peek() {
        if (children.isEmpty()) {
            return null;
        }
        return children.get(0);
    }

    public int serializeTo(OutputStream outputStream) throws IOException {
        int byteLen = 0;
        byteLen += ReadWriteForEncodingUtils.writeUnsignedVarInt(children.size(), outputStream);
        for (MetadataIndexEntry metadataIndexEntry : children) {
            byteLen += metadataIndexEntry.serializeTo(outputStream);
        }
        byteLen += ReadWriteIOUtils.write(endOffset, outputStream);
        byteLen += ReadWriteIOUtils.write(nodeType.serialize(), outputStream);
        return byteLen;
    }

    public static MetadataIndexNode deserializeFrom(ByteBuffer buffer) {
        List<MetadataIndexEntry> children = new ArrayList<>();
        int size = ReadWriteForEncodingUtils.readUnsignedVarInt(buffer);
        for (int i = 0; i < size; i++) {
            children.add(MetadataIndexEntry.deserializeFrom(buffer));
        }
        long offset = ReadWriteIOUtils.readLong(buffer);
        MetadataIndexNodeType nodeType =
                MetadataIndexNodeType.deserialize(ReadWriteIOUtils.readByte(buffer));
        return new MetadataIndexNode(children, offset, nodeType);
    }

    public Pair<MetadataIndexEntry, Long> getChildIndexEntry(String key, boolean exactSearch) {
        int index = binarySearchInChildren(key, exactSearch);
        if (index == -1) {
            return null;
        }
        long childEndOffset;
        if (index != children.size() - 1) {
            childEndOffset = children.get(index + 1).getOffset();
        } else {
            childEndOffset = this.endOffset;
        }
        return new Pair<>(children.get(index), childEndOffset);
    }

    int binarySearchInChildren(String key, boolean exactSearch) {
        int low = 0;
        int high = children.size() - 1;

        while (low <= high) {
            int mid = (low + high) >>> 1;
            MetadataIndexEntry midVal = children.get(mid);
            int cmp = midVal.getName().compareTo(key);

            if (cmp < 0) {
                low = mid + 1;
            } else if (cmp > 0) {
                high = mid - 1;
            } else {
                return mid; // key found
            }
        }

        // key not found
        if (exactSearch) {
            return -1;
        } else {
            return low == 0 ? low : low - 1;
        }
    }
}
